Petroski on Engineering: Everyone Loves Good Design

The Zakim Bunker Hill Bridge, a cable-stayed span constructed in conjunction with Boston’s Big Dig highway relocation project, is an excellent example of how a distinctive design can become a symbol of a city. It is now virtually mandatory for people engaged in television interviews originating from Boston to be shown with that bridge as backdrop.

Among the most dramatic of newer cable-stayed bridges is the Millau Viaduct, which carries vehicle traffic high over France’s wide and deep Tarn Valley. The bridge’s roadway is so high off the ground that it appears on occasion to float above the clouds that form beneath it, but the bridge earns equal distinction for the gently arcing curve of its deck and its overall striking appearance. I have lost count of how many correspondents have sent me still and moving images they took while driving over this bridge, but I never tire of admiring their pictures.

Not all striking bridge designs are towering, long-span highway bridges. Many pedestrian bridges of exceptional aesthetic value have been designed and built in recent years. Among the most widely known is the London Millennium Bridge, the design of which was the collaborative effort of the Arup engineering firm, Foster and Partners architects, and the sculptor Anthony Caro. It resulted in a striking low-slung suspension bridge, which to many people is hardly recognizable as one. Unfortunately, the bridge became somewhat of an embarrassment when its walkway swayed so much that it had to be closed within three days of its opening. The problem was fixed by retrofitting the bridge with stiffening struts and dampers, and it has become one of the most popular new tourist attractions on the River Thames.

Among the most highly anticipated of new bridges is the replacement for the east span of the San Francisco -- Oakland Bay Bridge, which was damaged in the 1989 Loma Prieta earthquake. Rather than spend $1 billion to retrofit the old structure, the California Department of Transportation argued, the money could be better spent on a new and distinctive span. The centerpiece of the new bridge, whose final cost will likely exceed $6 billion, is an unusual structure -- a self-anchored suspension bridge, one over whose single tower cables are draped and then connected to the ends of the roadway. Expected to be completed next year, the structure is sure to bring bridge enthusiasts and their cameras to San Francisco Bay.

I expect I may be the recipient of some photos of the new Bay Bridge, and I will welcome them. Different people have different opportunities to see different structures from different perspectives under different environmental conditions. Unlike the fine art masterpieces hanging in a museum under controlled temperature, humidity, and lighting, bridges must be works for all seasons. And the best of them truly are.

One of the most stunning bridges in the world is the George Washington Bridge, spanning the Hudson between Fort Lee NJ and the upper section of Manhattan, with it's unique exposed tower superstructure, peeking over the trees as you drive south at the end of the Palisades Parkway, or welcoming you home with it's spectacular lighting as an old friend after a long day driving on I-80.

But, what is not well known is that the distinctive design of the GWB was, in fact, an accident: While the massive double-decked bridge was being built, they ran out of money for the exterior stone cladding. So, the question arose, "can we do without it?" and the structural Engineers went back to work, recalculating the loads, and the answer was a resounding YES!

And that is how one of America's most iconic bridges came to be, as fate would have it~

One of the most stunning bridges in the world is the George Washington Bridge, spanning the Hudson between Fort Lee NJ and the upper section of Manhattan, with it's unique exposed tower superstructure, peeking over the trees as you drive south at the end of the Palisades Parkway, or welcoming you home with it's spectacular lighting as an old friend after a long day driving on I-80.

But, what is not well known is that the distinctive design of the GWB was, in fact, an accident: While the massive double-decked bridge was being built, they ran out of money for the exterior stone cladding. So, the question arose, "can we do without it?" and the structural Engineers went back to work, recalculating the loads, and the answer was a resounding YES!

And that is how one of America's most iconic bridges came to be, as fate would have it~

Mydesign, thanks for that info. I'm glad to know that India has such a strong program of historical monument preservation, since there are so many periods of its history with beautiful architecture. I learned about those buildings, as well as the amazing civic planning of those ancient cities, many years ago and was impressed by the intelligence and beauty of the designs and of the engineering in such a distant past.

Ann, you are right. Whatever the things possible are preserved and keeping as monuments by the archeological department. Apart from Mohenjo-Daro and Harappa, all the buildings with more than 100 years old are preserving by government and archeological departments, irrespective of it's a private or public building.

Mydesign, if I remember correctly, you're in India, right? That country has some incredibly well-built, very ancient public structures and multi-story houses in Mohenjo-Daro and Harappa I've read about (and seen reconstructions of), from the Indus Valley civilization of a few thousand years ago. I don't know if they are still standing, fully or partially, but from the archaeological reconstructions I've seen they were both beautiful and well-engineered.

Ann, our ancient civil engineers and draftsman had done excellent works in designing and building bridges and roads without any analytical and design software/tools. They had used their brain and skills to complete the task, without depending any man made tools. In my country we had a more than a dozen of bridges built by the great British engineers in 19th century. Still most of them are in good condition and public is widely using it and some other are protecting as heritage monuments.

Bob, those aqueducts that have lasted 2000-plus years are pretty amazing, aren't they? I've seen lots of good illustrations that show how they work, but none about the exact building methods used. Does anyone else know any?

I have add in my two cent to this architectural love-fest on bridges. There is something magical about the way they "work" without actually "doing" anything. Sort of like the human equivalent of a spider's web - constantly balancing forces through a series of aesthetic arcs and supports. All in plain view. Thanks for highlighting these marvels of engineering.

Ann, I agree completely. In 2009 my wife and I traveled to Madrid to celebrate our 40th anniversary. While there, we took a side trip to visit Toledo, an ancient city with many extrodanary structures, one being an aqueduct running close to three miles in length. The workmanship was stunning and how the engineers accomplished the uniform downward slope with the tools they had at their disposal amazes me. The stones were all laid by hand, each one carefully placed. Thousands upon thousands of carefully cut and placed stones. I would love to climb into Mr. Peabody's way-back machine just to see how some of these ancient monuments were constructed. It would certainly be a real treat.

Industrial workplaces are governed by OSHA rules, but this isn’t to say that rules are always followed. While injuries happen on production floors for a variety of reasons, of the top 10 OSHA rules that are most often ignored in industrial settings, two directly involve machine design: lockout/tagout procedures (LO/TO) and machine guarding.

Load dump occurs when a discharged battery is disconnected while the alternator is generating current and other loads remain on the alternator circuit. If left alone, the electrical spikes and transients will be transmitted along the power line, leading to malfunctions in individual electronics/sensors or permanent damage to the vehicle’s electronic system. Bottom line: An uncontrolled load dump threatens the overall safety and reliability of the vehicle.

While many larger companies are still reluctant to rely on wireless networks to transmit important information in industrial settings, there is an increasing acceptance rate of the newer, more robust wireless options that are now available.

To those who have not stepped into additive manufacturing, get involved as soon as possible. This is for the benefit of your company. When the new innovations come out, you want to be ready to take advantage of them immediately, and that takes knowledge.

Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.